U.S. patent number 8,734,205 [Application Number 12/637,533] was granted by the patent office on 2014-05-27 for rigid or flexible, macro-porous abrasive article.
This patent grant is currently assigned to Saint-Gobain Abrasifs, Saint-Gobain Abrasives, Inc.. The grantee listed for this patent is Anthony C. Gaeta, Paul S. Goldsmith, Kamran Khatami, James J. Manning. Invention is credited to Anthony C. Gaeta, Paul S. Goldsmith, Kamran Khatami, James J. Manning.
United States Patent |
8,734,205 |
Goldsmith , et al. |
May 27, 2014 |
Rigid or flexible, macro-porous abrasive article
Abstract
A macro-porous abrasive article includes a spun lace substrate
having a macro-porous structure and a coating. The coating is made
of a resin binder and abrasive aggregates. The abrasive aggregates
are formed from a composition of abrasive grit particles and a
nanoparticle binder. The coating is at least partially embedded in
the substrate. A method for making the macro-porous abrasive
article includes combining abrasive aggregates of abrasive grit
particles and a nanoparticle binder with a resin binder to form a
slurry. The slurry is applied to a macro-porous support structure
so that the slurry at least partially penetrates the substrate. The
resin is then cured to bond the aggregate grains to the
substrate.
Inventors: |
Goldsmith; Paul S. (Stow,
MA), Gaeta; Anthony C. (Lockport, NY), Manning; James
J. (Braintree, MA), Khatami; Kamran (East Greenwich,
RI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Goldsmith; Paul S.
Gaeta; Anthony C.
Manning; James J.
Khatami; Kamran |
Stow
Lockport
Braintree
East Greenwich |
MA
NY
MA
RI |
US
US
US
US |
|
|
Assignee: |
Saint-Gobain Abrasives, Inc.
(Worcester, MA)
Saint-Gobain Abrasifs (Conflans-Sainte-Honorine,
FR)
|
Family
ID: |
42266808 |
Appl.
No.: |
12/637,533 |
Filed: |
December 14, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100159805 A1 |
Jun 24, 2010 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61203422 |
Dec 22, 2008 |
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Current U.S.
Class: |
451/41; 451/532;
451/536; 451/533 |
Current CPC
Class: |
B24D
3/32 (20130101); B24B 7/182 (20130101); B24D
11/00 (20130101) |
Current International
Class: |
B24B
1/00 (20060101) |
Field of
Search: |
;451/41,530,532,533,536,539,544,548 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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Jun 1994 |
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CN |
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101068656 |
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Nov 2007 |
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CN |
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101267915 |
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Sep 2008 |
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CN |
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1339531 |
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Aug 2007 |
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EP |
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10-202538 |
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Aug 1998 |
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JP |
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2003011068 |
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Jan 2003 |
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JP |
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2003062754 |
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Mar 2003 |
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JP |
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2003071729 |
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Mar 2003 |
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JP |
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2005522341 |
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Jul 2005 |
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WO 9201536 |
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Feb 1992 |
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WO |
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0238338 |
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May 2002 |
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WO |
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Other References
PCT/US2009/067914: Notification of Transmittal of the International
Search Report and the Written Opinion of the International
Searching Authority, or the Declaration dated Jul. 26, 2010. cited
by applicant .
PCT/US2009/067914: International Search Report dated Jul. 26, 2010.
cited by applicant .
PCT/US2009/067914: Written Opinion of the International Searching
Authority dated Jul. 26, 2010. cited by applicant .
PCT/US2009/067914: Notification Concerning Transmittal of
International Preliminary Report on Patentability dated Jul. 7,
2011. cited by applicant.
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Primary Examiner: Rachuba; Maurina
Attorney, Agent or Firm: Sullivan; Joseph P. Abel Law Group,
LLP
Parent Case Text
RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application
No. 61/203,422, filed on Dec. 22, 2008. The entire teachings of the
above application are incorporated herein by reference.
Claims
What is claimed is:
1. A macro-porous abrasive article, comprising: a) a non-woven
substrate comprising hydro-entangled fibers having a macro-porous
structure including macropores having a pore size between about 15
microns to about 3 mm; and b) a coating on the macroporous
substrate, the coating including a binder and green, unfired
abrasive aggregates having a generally spheroidal or toroidal shape
that are formed from a composition of abrasive grit particles and a
nanoparticle binder, wherein the coating is at least partially
embedded in the macroporous substrate.
2. The abrasive article of claim 1, wherein the article is
flexible.
3. The abrasive article of claim 1, wherein the article is rigid or
semi-rigid.
4. The abrasive article of claim 1, wherein the coating is fully
embedded in the substrate.
5. The abrasive article of claim 1, further comprising additional
abrasive particles over the coating.
6. The abrasive article of claim 1, further comprising an
anti-loading/dispersing agent.
7. The abrasive article of claim 1, wherein the binder is an ultra
violet light curable acrylate.
8. The abrasive article of claim 1, wherein the green, unfired
aggregates are essentially filled.
9. The abrasive article of claim 8, wherein the green, unfired
aggregates comprise about 21% by weight bond.
10. The abrasive article of claim 1, wherein the macro-porous
substrate is patterned.
11. A method of forming a macro-porous abrasive article, comprising
the steps of: a) combining abrasive aggregates with a resin binder
to form a slurry, wherein the abrasive aggregates are green,
unfired abrasive aggregates having a generally spheroidal or
toroidal shape that are formed from a composition of abrasive grit
particles and a nanoparticle binder; b) applying the slurry to a
non-woven substrate comprising hydro-entangled fibers having a
macro-porous structure to at least partially penetrate the
substrate, wherein the macro-porous structure includes macropores
having a pore size between about 15 microns to about 3 mm; and c)
curing the resin to bond the aggregate grains to the substrate.
12. The method of claim 11, wherein the slurry fully penetrates the
substrate.
13. The method of claim 11, wherein the slurry is applied to the
substrate by gravure coating, roll coating, or transfer
coating.
14. The method of claim 11, further comprising the step of applying
a grain coating after applying the slurry to the substrate.
15. The method of claim 14, wherein the grain coating is applied by
gravity, slurry, electrostatic coating or electrostatic spray.
16. The method of claim 11, wherein the resin binder is an
acrylate.
17. The method of claim 16, wherein the acrylate resin binder is
cured by ultra violet light.
18. The abrasive article of claim 11, wherein the macro-porous
substrate is patterned.
19. The abrasive article of claim 11, wherein the macro-porous
substrate is non-woven.
20. A method for abrading a work surface, comprising applying an
abrasive product in an abrading motion to remove a portion of the
work surface, the abrasive product including: a) a nonwoven
substrate comprising hydro-entangled fibers having a macro-porous
structure including macropores having a pore size between about 15
microns to about 3 mm; and a coating on the macroporous substrate,
the coating including a binder and green, unfired abrasive
aggregates having a generally spheroidal or toroidal shape that are
formed from a composition of abrasive grit particles and a
nanoparticle binder, wherein the coating is at least partially
embedded in the macroporous substrate.
Description
BACKGROUND OF THE INVENTION
High performance abrasive particles for use in finishing and
polishing include grit particles and composite particles. Grit
particles are solid grains, while composite particles are formed
from an aggregate of small primary grit particles bound together
within a nanoparticle binder.
Conventionally, when grit particles are used to finish or polish a
surface to a desired smoothness, the polishing process occurs in
several polishing steps using abrasive grains of varying grit size.
Each successive polishing step involves the use of grit particles
of decreased size. The surface is first polished with a relatively
coarse abrasive material and then polished again with a somewhat
finer grit abrasive material. This process may be repeated several
times, which each successive re-polishing being carried out with a
progressively finer grit abrasive until the surface is polished to
the desired degree of smoothness.
It has been found that use of composite particles offer the
efficiency of achieving comparable surface smoothness in fewer
steps, or in even only a single polishing step. It is believed that
the primary particles, the nanoparticle binder, and the aggregate
as a whole each achieve the steps of polishing necessary to obtain
the final desired surface smoothness. Composite particles are
therefore favored in applications requiring fast ultra-fine
polishing.
Nevertheless, a need exists for an abrasive article and a method of
polishing that achieves improved surface smoothness and longer
product life.
SUMMARY OF THE INVENTION
In one aspect the invention is directed to a macro-porous abrasive
article that includes a patterned non-woven spun lace substrate
having a macro-porous structure and a coating. The coating is made
of a resin binder and abrasive aggregates. The abrasive aggregates
are formed from a composition of abrasive grit particles and
nanoparticle binder. The coating is at least partially embedded
into the substrate.
In another aspect, the invention is directed to a method of forming
a macro-porous abrasive article. The method includes combining
abrasive aggregates formed from abrasive grit particles in a
nanoparticle binder with a resin binder to form a slurry. The
slurry is then applied to a patterned non-woven spun lace substrate
having a macro-porous structure so that the slurry at least
partially penetrates the substrate. The resin is then cured to bond
the aggregate grain to the substrate.
The present invention has many advantages. For example, the
abrasive article of the invention includes a macroporous backing or
substrate that removes substantially either dry or wet swarf from a
workpiece during use. By doing so, "loading" or clogging that can
occur is significantly reduced, thereby extending the cutting life
of the abrasive article. Further, the abrasive article of the
invention can be rigid, such as is particularly suitable for
applications including drywall joint sanding, for example. The
abrasive article, in another embodiment, can be flexible, and is
suitable for applications such as ophthalmic lens finishing. Other
applications, where either flexible or semi-rigid abrasive articles
of the invention can be employed, are automotive clear coat
finishing and automotive primer finishing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-3 are photomicrographs taken with a scanning electron
microscope showing abrasive aggregates including diamond grit
combined with silica nanoparticles in a coating on a substrate;
FIGS. 4-6 are photomicrographs taken with a scanning electron
microscope showing abrasive aggregates including silicon carbide
grit combined with silica nanoparticles in a coating on a
substrate;
FIG. 7 is a drawing of a patterned macro-porous substrate;
FIG. 8 shows a performance comparison of two different backings for
the abrasive article;
FIG. 9 shows a performance comparison of two different degrees of
silicon carbide bonding in the abrasive grit particles.
DETAILED DESCRIPTION OF THE INVENTION
The foregoing will be apparent from the following more particular
description of example embodiments of the invention, as illustrated
in the accompanying drawings in which like reference characters
refer to the same parts throughout the different views. The
drawings are not necessarily to scale, emphasis instead being
placed upon illustrating embodiments of the present invention. The
teachings of all patents, published applications and references
cited herein are incorporated by reference in their entirety.
Described in detail below are the components of various embodiments
of the abrasive article of the invention.
The abrasive article of the invention includes a patterned
macroporous substrate, a resin binder, and abrasive aggregates. The
abrasive aggregates include abrasive grit particles and a
nanoparticle binder.
Macroporous Substrate
In one embodiment, the macroporous substrate of the abrasive
article of the invention is formed from fibers that have been bound
to form a nonwoven web. The fibers can be interlocked by a suitable
method known in the art, such as needle punching and
hydro-entanglement. Hydro-entangled webs are also known as "spun
lace." In some embodiments, the substrate can be hydro-entangled
with a velour attachment system to create a composite substrate
with lint free attachability to the polishing tooling. The fibers
of the substrate can be continuous or staple fibers, monofilament
or multifilament, and can be formed from various materials,
including polymer fibers and plant fibers. In one embodiment, the
fiber is a polyester fiber. Other materials that can be used
include synthetic fibers such as polypropylene, polyethylene,
nylon, rayon, steel, fiberglass, or natural fibers, such as cotton
or wool. The fiber can be between about 100-2000 denier.
The substrate material is preferably flexible and can have a
thickness between about 300 micron and about 6 mm. The pattern of
the substrate can vary, but should include macropores, such as
those shown in FIG. 7. As used herein, the term "macroporous" means
having a pore size between about 15 microns to about 3 mm. These
macropores of the macroporous substrate not only reduce swarf
accumulation during the polishing operation, but also allow the
abrasive article to be compliant, so that it can conform to
irregular sanded shapes. In addition, the macropores allow fluids
and sanding swarf to flow through the web, preventing loading of
the abrasive article.
Abrasive Aggregate Particles
As used herein, the term "aggregate" may be used to refer to a
particle made of a plurality of smaller particles that have been
combined in such a manner that it is relatively difficult to
separate or disintegrate the aggregate particle into smaller
particles by the application of pressure or agitation. This is in
contrast to the term "agglomerate," which is used to refer to a
particle made of a plurality of smaller particles which have been
combined in such a manner that it is relatively easy to
disintegrate into the smaller particles, such as by the application
of pressure or hand agitation. Generally, agglomerates form
spontaneously in slurry or in dispersion, while aggregates must be
formed by a specific method, such as those described in U.S. Pat.
No. 6,797,023 and U.S. patent application Ser. No. 12/018,589
entitled, "Coated Abrasive Products Containing Aggregates," of
Starling, filed on Jan. 23, 2008, the teachings of which are
incorporated herein in their entirety. The aggregates have a
composite structure, including both abrasive grits that have a size
within the microparticle range, and a nanoparticle binder that
provides the matrix of the aggregate in which the abrasive grits
are embedded or contained.
Typically, the aggregates are utilized in the abrasive material
without notable post-formation heat treatment, such as calcining,
sintering, or recrystallization, which alters the crystallite size,
grain size, density, tensile strength, young's modulus, and the
like of the aggregates. Such heat treatment processes are commonly
carried out in ceramic processing to provide usable products, but
are not utilized herein. Such heat treatment steps are generally
carried out in excess of about 400.degree. C., generally about
500.degree. C. and above. Indeed, temperatures can easily range
from about 800.degree. C. to about 1200.degree. C. and above for
certain ceramic species.
When viewed under magnification, the aggregates have a generally
spheroidal shape, being characterized as rounded or spherical as
seen in the scanning electron micrographs of FIGS. 4-6. In some
instances, however, the aggregates may be observed to have a void
near the center of the aggregate and thus exhibit a more toroid or
torus-like shape as seen in the scanning electron micrographs of
FIGS. 1-3. Individual particles of the abrasive grit material, such
diamond grit, may be observed to be dispersed over the surface of
the aggregates and within the interior thereof, with relatively few
instance of the individual grit particles clumping together on the
surface of the aggregate. It is noted that FIGS. 1-6 show
dispersed, individual aggregates that are bound together in a resin
binder system.
The size and size range of the aggregates may be adjusted and may
depend on many factors, including the composition of the mixture
and, if a spray dryer is used in aggregate formation, the spray
dryer feed rate. For example, abrasive aggregates of sizes
including those of approximately 20 microns, 35 microns, 40
microns, and 45 microns can be produced using a spray dryer. These
aggregates can include abrasive grit particles ranging from about 5
to about 8 microns.
Further study of the abrasive aggregates has revealed that certain
spheroids are hollow, while others are essentially filled with
grain and/or nanoparticle binder. Hollow particles can be
analogized to thick-shelled racquet balls, having a wall thickness
within a range of about 0.08 to about 0.4 times the average
particle size of the aggregates. Process parameters and
compositional parameters can be modified to effect different wall
thicknesses. In some embodiments, the abrasive agglomerates are
those described in U.S. Pat. No. 6,797,023 and U.S. patent
application Ser. No. 12/018,589 entitled, "Coated Abrasive Products
Containing Aggregates," of Starling, filed on Jan. 23, 2008, the
teachings of which are incorporated herein in their entirety.
Abrasive Grit Particles
The abrasive grit particles that form the aggregate composite
particle generally have a Mohs hardness of greater than about 3,
and preferably from about 3 to about 10. For particular
applications, the abrasive grit particles have a Mohs hardness not
less than about 5, 6, 7, 8, or 9. The abrasive grit particles are
generally believed to serve as the primary active grinding or
polishing agent in the abrasive aggregates. Examples of suitable
abrasive compositions include non-metallic, inorganic solids such
as carbides, oxides, nitrides and certain carbonaceous materials.
Oxides include silicon oxide (such as quartz, cristobalite and
glassy forms), cerium oxide, zirconium oxide, aluminum oxide.
Carbides and nitrides include, but are not limited to, silicon
carbide, aluminum, boron nitride (including cubic boron nitride),
titanium carbide, titanium nitride, silicon nitride. Carbonaceous
materials include diamond, which broadly includes synthetic
diamond, diamond-like carbon, and related carbonaceous materials
such as fullerite and aggregate diamond nanorods. Materials may
also include a wide range of naturally occurring mined minerals,
such as garnet, cristobalite, quartz, corundum, feldspar, by way of
example. Certain embodiments of the present disclosure, take
advantage of diamond, silicon carbide, aluminum oxide, and/or
cerium oxide materials, with diamond being shown to be notably
effective. In addition, those of skill will appreciate that various
other compositions possessing the desired hardness characteristics
may be used as abrasive grit particles in the abrasive aggregates
of the present disclosure. In addition, mixtures of two or more
different abrasive grit particles can be used in the same
aggregates. Silicon carbide has been found to be particularly
effective as a grit particle for use in the present abrasive
article. In particular, the silicon carbide is preferably about 21%
by weight bonded, but can range between about 10% and about 80% by
weight bonded.
As should be understood from the foregoing description, a wide
variety of abrasive grit particles may be utilized in embodiments.
Of the foregoing, cubic boron nitride and diamond are considered
"superabrasive" particles, and have found widespread commercial use
for specialized machining operations, including highly critical
polishing operations. Further, the abrasive grit particles may be
treated so as to form a metallurgical coating on the individual
particles prior to incorporation into the aggregates. The
superabrasive grits are particularly suitable for coating. Typical
metallurgical coatings include nickel, titanium, copper, silver and
alloys and mixtures thereof.
In general, the size of the abrasive grit particles lies in the
microparticle range. As used herein, the term "microparticle," may
be used to refer to a particle having an average particle size of
from about 0.1 microns to about 50 microns, preferably not less
than about 0.2 microns, about 0.5 microns, or about 0.75 microns,
and not greater than about 20 microns, such as not greater than
about 10 microns. Particular embodiments have an average particle
size from about 0.5 microns to about 10 microns. The size of the
abrasive grit particles can vary upon the type of grit particles
being used. For example, diamond grit particles can have the size
of about 0.5 to about 2 microns, silicon carbide grit particles can
have the size of about 3 to about 8 microns, and aluminum oxide
grit particles can have a size of about 3 to about 5 microns.
It should be noted that the abrasive grit particles can be formed
of abrasive aggregates of smaller particles such as abrasive
aggregate nanoparticles, though more commonly the abrasive grits
are formed of single particles within the microparticle range. As
used herein, the term "nanoparticle," may be used to refer to a
particle having an average particle size of from about 5 nm to
about 150 nm, typically less than about 100 nm, 80 nm, 60 nm, 50
nm, or less than about 50 nm. For instance, a plurality of
nano-sized diamond particles may be aggregated together to provide
a microparticle of diamond grit. The size of the abrasive grit
particles can vary depending upon the type of grit particles being
used.
The abrasive grit particles may, in general, constitute between
about 0.1% to about 85% of the aggregates. The aggregates more
preferably include between about 10% to about 50% by weight of the
abrasive grit particles.
The abrasive aggregates may be formed using a single size of
abrasive grit particle, the size of the grit particle and the
resultant aggregates both being tailored to the desired polishing
application. In the alternative, mixtures of two or more
differently sized abrasive grit particles may be used in
combination to form abrasive aggregates having advantageous
characteristics attributable to each of the grit particle
sizes.
Nanoparticle Binder
The abrasive aggregates according to the present disclosure also
include a nanoparticle binder material as stated above. The
nanoparticle binder generally forms a continuous matrix phase that
functions to form and hold the abrasive grit particles together
within the abrasive aggregates in the nature of a binder. In this
respect, it should be noted that the nanoparticle binder, while
forming a continuous matrix phase, is itself generally made up of
individually identifiable nanoparticles that are in intimate
contact, interlocked and, to a certain extent, bonded with each
other. However, due to the green, unfired state of the thus formed
aggregates, the individual nanoparticles are generally not fused
together to form grains, as in the case of a sintered ceramic
material. As used herein, description of nanoparticle binder
extends to one or multiple species of binders.
The nanoparticle binder material may comprise very fine ceramic and
carbonaceous particles such as nano-sized silicon dioxide in a
liquid colloid or suspension (known as colloidal silica).
Nanoparticle binder materials may also include, but are not limited
to, colloidal alumina, nano-sized cerium oxide, nano-sized diamond,
and mixtures thereof. Colloidal silica is preferred for use as the
nanoparticle binder in certain embodiments of the present
disclosure. For example, commercially available nanoparticle
binders that have been used successfully include the colloidal
silica solutions BINDZEL 2040 BINDZIL 2040 (available from Eka
Chemicals Inc. of Marietta, Ga.) and NEXSIL 20 (available from
Nyacol Nano Technologies, Inc. of Ashland, Mass.).
The abrasive aggregates also can include another material which
serves primarily as a plasticizer, also known as a dispersant, to
promote dispersion of the abrasive grit within the aggregates. Due
to the low processing temperatures used, the plasticizer is
believed to remain in the aggregates, and has been quantified as
remaining by thermal gravimetric analysis (TGA). The plasticizer
might also assist in holding together the grit particles and
nanoparticle binder material in an aggregate when the mixture is
spray-dried.
Plasticizers include both organic and inorganic materials,
including surfactants and other surface tension modifying species.
Particular embodiments make use of organic species, such as
polymers and monomers. In an exemplary embodiment, the plasticizer
is a polyol. For example, the polyol may be a monomeric polyol or
may be a polymeric polyol. An exemplary monomeric polyol includes
1,2-propanediol; 1,4-propanediol; ethylene glycol; glycerin;
pentaerythritol; sugar alcohols such as malitol, sorbitol, isomalt,
or any combination thereof; or any combination thereof. An
exemplary polymeric polyol includes polyethylene glycol;
polypropylene glycol; poly (tetramethylene ether) glycol;
polyethylene oxide; polypropylene oxide; a reaction product of
glycerin and propylene oxide, ethylene oxide, or a combination
thereof; a reaction product of a diol and a dicarboxylic acid or
its derivative; a natural oil polyol; or any combination thereof.
In an example, the polyol may be a polyester polyol, such as
reaction products of a diol and a dicarboxylic acid or its
derivative. In another example, the polyol is a polyether polyol,
such as polyethylene glycol, polypropylene glycol, polyethylene
oxide, polypropylene oxide, or a reaction product of glycerin and
propylene oxide or ethylene oxide. In particular, the plasticizer
includes polyethylene glycol (PEG).
Forming the Abrasive Article
The coating of the abrasive article is initially a slurry of
abrasive aggregates and a binder used to adhere the aggregates onto
a surface of a substrate. The binder is preferably a polymeric
resin binder. Suitable polymeric resin materials include
polyesters, epoxy resins, polyurethanes, polyamides, polyacrylates,
polymethacrylates, polyvinyl chlorides, polyethylene, polysiloxane,
silicones, cellulose acetates, nitrocellulose, natural rubber,
starch, shellac, and mixtures thereof. The polymeric resin may be
cured by heat or other radiation. Most preferably, the resin is a
U.V. curable acrylate resin.
In addition to the aggregates and binder, the slurry generally also
includes a solvent such as water or an organic solvent and a
polymeric resin material. The slurry may additionally comprise
other ingredients to form a binder system designed to bond the
aggregate grains onto a substrate. The slurry composition is
thoroughly mixed using, for example, a high shear mixer.
The aggregates, resin and optional additives are combined together
to form the slurry, and the slurry is coated onto the substrate to
at least partially penetrate the substrate. The slurry is
preferably applied to the substrate using a blade spreader to form
a coating. Alternatively, the slurry coating may be applied using
slot die, roll, transfer, gravure, or reverse gravure coating
methods. As the substrate is fed under the blade spreader at a
desired coat speed, the aggregate grain slurry is applied to the
substrate in the desired thickness.
The abrasive article can be flexible, semi-rigid, or rigid,
depending on how much the aggregate coating penetrates the
substrate. Partial penetration yields a flexible abrasive article,
while complete penetration of the coating yields a rigid or
semi-rigid abrasive article. As used herein, the term "rigid,"
means deformable or bendable to as small as about a 3 inch radius.
As used herein, the term "semi-rigid," means deformable or bendable
to about as small as a 1 inch radius. As used herein, the term
"flexible" means deformable or bendable to as small as about a 1/4
inch radius.
Optionally, additional abrasive particles can be added over the
aggregate coating using various grain application methods, such as
gravity application, slurry, electrostatic coating, or
electrostatic spray. In addition, an antiloading or dispersing
agent can be added to the abrasive article to further minimize the
accumulation of swarf.
The coated substrate is then cured by heating or radiation to
harden the resin and bond the aggregate grains to the substrate. In
one embodiment, the coated substrate is heated to a temperature of
between about 100.degree. C. and about 250.degree. C. during this
curing process. In another embodiment of the present disclosure, it
is preferred that the curing step be carried at a temperature of
less than about 200.degree. C. In yet another embodiment, the
coating is cured by U.V. radiation.
Once the resin is cured and the aggregate abrasive grains are
bonded to the substrate, and the coated substrate may be used for a
variety of stock removal, finishing, and polishing applications. A
work surface can be abraded by applying the finished abrasive
product in an abrading motion to remove a portion of a work
surface. A description of example embodiments of the invention
follows.
EXAMPLES
Two types of backing, PET (polyethylene terepthalate) film and a
macroporous substrate (PGI Spun Lace M059 scrim) were tested for
abrasion performance on identical AAA 1.25'' test panels. The PET
film-backed and macroporous substrate-backed abrasive articles
included the same coating, which included a U.V. acrylate binder
resin mixed with abrasive aggregates formed from silicon carbide
grit particles and a nanoparticle binder resin.
Performance results, such as the number of spots before exhaustion
("No. Spots"), average surface roughness ("Ra") and number of
pigtails ("#PT's") were recorded and are shown in the bar chart in
FIG. 8. The number of spots before exhaustion indicates the useful
life duration of the test article. An abrasive test sample is used
to abrade and remove surface defects on as many surface spots as
possible before surface defects are no longer removed; the greater
number of spots before exhaustion, the longer the useful life of
the test article. Surface roughness is measured by a surface
profilometer, in this case, the Mahr Perthometer M2 (Manufactured
by Mahr GmbH Gottingen). A smooth surface is desirable. Pig-tails
are deep spiral shaped scratches formed by the abrasive article
during abrasion, and their presence is undesirable. The table
indicates that UV acrylate slurry coatings on the macroporous
substrate (PGI Spun Lace M059 scrim) perform significantly better
than those on the PET film, as the scrim exhibited greater number
of spots before exhaustion, less surface roughness, and absence of
pig-tails.
As indicated in FIG. 8, macroporous substrate backing exhibits
superior grinding performance in comparison to PET film backing in
an abrasive aggregate system. This can also be observed by way of
the maximum surface roughness after grinding, "Rmax." Table 1 below
provides maximum surface roughness values for test abrasive
articles similar to those described above.
TABLE-US-00001 TABLE 1 Comparison of Rmax for PET film and Scrim
backings Backing Rmax (n1) Rmax (n2) Rmax (n3) Average PET Film 79
163 179 140 Scrim (PGI Spun 66 66 66 66 Lace M059)
For aggregates containing silicon carbide abrasive grit particles,
two different degrees of bonding were also tested. The first
abrasive article tested had silicon carbide grit particles that
were 21% bonded. The second abrasive article tested had silicon
carbide grit particles that were 47% bonded. In the bar chart of
FIG. 9, the 21% bonded silicon carbide is shown to give an
advantage in the total number of spots.
While this invention has been particularly shown and described with
references to example embodiments thereof, it will be understood by
those skilled in the art that various changes in form and details
may be made therein without departing from the scope of the
invention encompassed by the appended claims.
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